What is the Y in 480Y voltage?

The Wye (also know as Star - especially in the motor rewind industry) is a 4-wire system which provides two different supply voltages. The center-point of the Wye is the system neutral and is usually solidly grounded. Where it is desirable to limit the phase-to-ground fault magnitude the center-point of the Wye may be connected to ground through and neutral grounding resistor or a current limiting reactor. Because the system is tied to ground it is easy to provide system ground fault protection. Three-phase loads can be connected phase-to-phase and singlephase loads can be connected from any phase to the system neutral. On a wye system, the phase unbalance currentis carried by the system neutral. On a Wye system the line current is equal to the phase current i.e. ( ILine 1 = IPhase A) and the line-to-line voltage is equal to the vector sum of two individual phase voltages i.e. (E Line1-2 = E PhaseA + E PhaseB' ). In a Wye system the phase-to-phase voltage is 1.732 x the phase-to-ground voltage. Some typical Wye system voltages are: 120/208Y, 277/480Y, 2400/4160Y, 4160/7200Y, 7200/12470Y, 7620/13200Y,and 19920/34500Y